152 Descriptions of new species of Leptcena and Cyclonema. 



Length of some large specimens about half an inch, breadth one inch ; 

 others are nearly as long as broad. 



The typical form was found about 150 feet above low water-mark of 

 the Ohio River, at Cincinnati, but varieties are found at other locali- 

 ties all through the Cincinnati Group. 



Cyclonema pyramidata — (James) . 



[Cyclonema pyramidata. — James. Catalogue of Lower Silurian Fossils, 1871.] 



Shell obliquely pyramidal ; broader than high ; base expanded ; 

 slope from apex to base quite regular ; volutions four, flat or slightly 

 depressed ; suture shallow ; a narrow, angular shoulder on the upper 

 edge of the first volution, in some cases ; surface ornamented by 

 revolving lines, about every fourth one, on the body whorl, much 

 stronger than the ones between, crossed by fine striie or lines of growth, 

 having a backward direction ; on the upper whorls every other one of 

 tlie revolving lines stronger than the intermediate one. The body 

 whorl makes a large portion of the shell ; slope of the vmder side to 

 the outer lip sharply rounded, to the inner lip and umbilicus nearly 

 flat, or rounding inward ; inner lip, of old specimen, thickened ; outer 

 lip thin, and sharp at the edge, and slightly projecting at the junction 

 with the outer line of the volution. Aperture rounded, or suboval- 



Breadth of a medium size specimen, 14 lines; height, 11 lines. 



This idiell bears some resemblance to C. bilix, Conrad, but it is 

 much more expanded at the base, and the volutions are flat or slightly 

 ■depressed, whilst in C bilix they are more or less inflated, and the 

 suture deeper, and the outline quite different. 



Position and Locality. — Cincinnati Group, about 350 or 400 feet 

 above low water-mark of the Ohio River, at Cincinnati ; but it may be 

 found at other localities and at different horizons. 



Cyclonema j^MciMate—( James) . 



[Cyclonfma fluctuaia. — James. Catalogue of Lower Silurian Fossils, 1871.] 

 [ Cyclonema bilix var. lata. — Meek. Palffiontology of Ohio, 1873.] 



\_Fluctuata referring to the wavy surface.] 



Shell turbinate, depressed ; breadth greater than the length ; volu- 

 tions four or five increasing rapidly in size, the first one flattened on 

 the under side ; aperture suboval, oblique ; suture broad and deep ; 

 inner lip thickened, outer lip thin and sharp. Surface marked by 



